1. Field of the Invention
The present invention relates generally to a heat consumption meter for use in buildings and, in particular, a meter for determining the energy consumed for heating and cooling individual units in a multi-unit building using a central heating and/or cooling system.
2. Description of Prior Art
Known meters which have been used to meter heating and cooling energy consumption in individual units of a multi-unit building, such as an apartment building, using a central heating/cooling source are of two basic types. The first uses a time recording meter, or hour meter, to record the amount of time the room thermostat calls for heating or cooling. The proportionate energy consumption between units is related to the time each unit's thermostat and thus heat exchanger is on. U.S. Pat. Nos. 3,995,686 and 4,049,044 disclose the use of this type of hour meter. The second type is commonly called a BTU meter and consists of a flowmeter to record the amount of water flow through a heat exchanger and two temperature sensors to measure and record the difference in input and output water temperatures from the heat exchanger. These two quantities are multiplied together to determine the amount of energy transferred to or from the heat exchanger via the water supply. Meters of this type have been available for many years and may be mechanical or electromechanical in construction.
The use of hour meters to meter heat suffers from severe limitations. In general, there is a very poor correlation between the amount of time a unit's thermostat or heat exchanger is on and the amount of heating or cooling energy consumed. This is due to variations in each zone of a central heating/cooling system and varying environmental conditions in each unit which cause heat exchangers to have unequal heat transfers for the same amount of operating time. Thus, the reading of an hour meter is not an accurate indication of individual unit heating and/or cooling energy consumption.
Generally, BTU meters are very accurate but are difficult to install and quite expensive, relatively complex, and subject to wear, failure, and inaccuracies in their moving parts. This has prevented their widespread use. In addition to BTU and hour meters there is one other device which is used to meter heat consisting of a glass capillary tube filled with alcohol which evaporates at a rate proportional to the temperature of the heat exchanger to which it is affixed. These meters offer poor accuracy and are cumbersome to read and to use. Also, the individual units must be entered to retrieve, read, and replace these meters. This is desirable to neither the building owners or the occupants.
The present invention proposes to provide a new heat meter which is accurate yet inexpensive in construction and provides remote reading for the convenience of building owners and occupants. The meter uses solid state electronics and temperature sensors to sense heat transfer rates and an electronic pulse generator to totalize these heat transfer amounts on a counter which can be located some distance away from the unit being metered for the convenience of remote meter reading. Installation does not require interrupting heating or cooling service to the unit nor cutting into piping. Accuracy is very high being limited only to the precision of the sensors and electronics used in the device.
It is an object of this invention to provide an aparatus for accurately and economically monitoring the heating and cooling energy consumed in a unit of a multi-unit building.
Other objects will in part be obvious and will in part appear hereinafter.